Control device with hydraulic synchronising control for forging machines

ABSTRACT

A control device for forging machines having a plurality of hydraulically actuated forging tools for reducing the cross section of a workpiece. In order to increase the forging accuracy the actual characteristic of each forging tool at the end of the forging stroke is compared with a predetermined characteristic and, when the characteristics differ, a servo-control mechanism supplies pressure fluid to or withdraws it from the line interconnecting a pump cylinder of the drive mechanism with the respective forging tool.

United States Patent 1191 Guse 1111 3,841,125 1451 Oct. 15, 1974 CONTROL DEVICE WITH HYDRAULIC SYNCHRONISING CONTROL FOR FORGING MACHINES [75] Inventor: Rudolf Siegfried Guse,

Dusseldorf-Rath, Germany [73] Assignee: Maschinenfabrik Sack GmbII,

Dusseldorf, Germany 22 Filed: Feb. 16, 1973 21 Appl. No.: 333,378

[30] Foreign Application Priority Data Mar; 18, 1972 Germany 2207717 [52] U.S.'Cl 72/21, 72/19, 72/28, 7 72/402, 72/453 [51] Int. Cl..'.' B2lb 37/08 [58] Field of Search 72/8, 19, 20, 2 1, 28, 402, 72/453, 443, DIG. 4, DIG. 5

[56] References Cited I UNITED STATES PATENTS 3,031,903 5/1962 Billen et al 72/443 3,196,647 7/1965 Schneider 72 21 3222912 12/1965 Specht 7'2/402 3,224,244 12 1965 Kralow ctz... 72 402 3,246,502 4 1966 Brignoli 72 400 3,415,105 12/1968 Brown et al. 72 402 3,478,565 11/1969 Schenk ct al. 72 399 3,613.432 10/1971 Schenk ct a1 72/399 3,657,916 4/1972 Pahnkc'. 72/399 Primary Examiner-Charles W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firmlohn J. Dennemeyer 5 7 ABSTRACT A control device for forging machines having a plurality of hydraulically actuated forging tools for reducing the cross section of a workpiece. In order to increase the forging accuracy the actual characteristic of each forging tool at the end of the forging stroke is compared with a predetermined characteristic and, when the characteristics differ, a servo-control mechanism supplies pressure fluid to or withdraws it from the line interconnecting a pump cylinder of the drive mechanism with the respective forging tool.

7 Claims, 1 Drawing Figure CONTROL DEVICE WITH HYDRAULIC SYNCHRONISING CONTROL FOR FORGING I MACHINES I The'invention relates to a control'device with hydraulic synchronising control for forging machines having a plurality of pressure cylinders which are associated with forging saddles surrounding the workpiece,

sition of the forging saddle and a controller which cor'nv pressure side of the operating cylinder for effecting dis- I placement of thestroke position of the operating piston of the operating cylinder or for compensating leakage losses. A separate filling pump'serves for replenishing the retraction end of the double acting operating cylinder. The drive proper of the operating cylinder of the forging machine consists of piston pumps disposed in pairs for respective pairs of" forging saddles, these pumps having pistons of different diameters, the pistons of larger'diameter serving for loading the pressure side and the pistons of smaller diameter serving for loading the retraction .side of the operating pistons.

The preselected nominal values can be attained during forging by the control pump in conjunction with the electrical control but the expense involved is very high, since, apart from the control pumps, which have a reversible feed direction and which are therefore very expensive, and the additional filling pumps for loading the retraction side of the operating cylinders, an overpressure valve must additionally be present in each system. Furthermore, in the known machine the forging saddles cannot be stopped without the driving arrangement being disconnected. .Although a certain interchange of pressure liquid is effected by the control pump in the event of leakage lossesthis interchange is so small that an effective cooling of the operating liquid is not obtained-The most important disadvantage of the known machine, however, is that the stroke posifor forging machines'of the kind referred to above,. which is simple ,in construction and-yet ensures-a functionally reliable adjustment of control of the operating pistons. This object is achieved according to the invention in that the hydraulic servo-device comprises, for each forging saddle, a reversible compensating cylinder which is connected to the connecting pipe which extends'between the pressure side of the operating cylinder and the pump cylinder. Such a reversible compensating cylinder can be produced considerably more economically than a'control pump with a two directional feed and at the same time the advantage is ob-.

tained that it replaces not only the control pumpnormally present on the pressure side of the operating cylinder but also the filling pump present onthe retraction side. Therefore, necessary correction of the stroke position of the operating pistons can be performed in a simple manner by means of the compensating cylinder, and any leakage losses which may occur can also be compensated very easily. 7

Preferably the compensating cylinder comprises an adjustable piston which separates twoworking spaces from one another, and which has a piston rod which extends into a control chamber connected to the connect ing pipe. The quantity of liquid located in the connecting pipe between the operating cylinder and the pump cylinder can be controlled very accurately by means of this piston rod, in that the piston carrying the piston rod is adjusted appropriately,'so that either pressure liquid is pressed into the connecting pipe or a larger space is made available in the control space for the quantity of liquidlocated in' the pipe by a return of the piston rod so that a corresponding relief occurs. In this case the operating piston is displaced into its new stroke position under the effect of the substantially constant retraction force. 1 v

The control of the compensating cylinder, can-be realised. very simply in that the two operating spaces thereof can be selectively connectedto a control pump by means of a control valve. The piston can thus be ad- 1 justed within the compensatingcylinder inaccordance with the desired pressure adjustment in the connecting pipe-Preferably the control valve is electrically connected to the controller, which in turn is connected directly'to the transmitter disposed at the forging saddle. Owing to this direct sensing of the position of the forging saddle, and exact displacement of the servo valve is ensuredby'means of the electrical control and thus a change of the pressure'means supply in the connect ing pipe is ensured which depends exactly upon the forging saddle, i.e., the forging-dimension.

ln'one embodiment of the invention, the transmitter co-operates with a pinion which engages in a tooth rack located at the free end of a lever attached to the pivot pin -of the forging saddle.

The controller may be connected to afurther actual value transmitter which co-operates with a position indicator which is disposed on a further piston rod located opposite the piston rod of the compensating cylinder'and projecting from the latter. This actual value transmitter constitutes a position monitor for the piston in the compensating cylinder and thus acts as a correcting device for incorrect quantities. v s

The controller moreover, is connected'to, further.

transmitters, i.e. to a transmitter indicating the forward end position of the driving arrangement, constructed as' a crankdrive, and a transmitter determining the liquid pressure in the connecting pipe between the operating cylinder and the pressure cylinder. The first mentioned transmitter ensures that the comparison between the nominal value and the actual value takes place only when the crank drive has attained its forward end positon, that is to say the full pressure is present in the connecting pipe and thus the forging saddle is located in its farthest possible forging position, whereas, the second transmitter can deliver the impulse for the servo valve only, when the pressure in'the connecting pipe is low, i.e., has dropped substantially to zero, since only then a simple displacement of the piston in the compensating cylinder is possible, because otherwise the piston would have to be displaced against the high pressure in the connecting pipe. I

A preferred embodiment of the invention is illustrated in the drawing, which is a diagrammatic representation of a forging saddle and associated hydraulic control device of a forging machine having, for example, four forging saddles which are displaced by 90 relatively to each other and which enclose on all sides a workpiece to be deformed, the other forging saddles and their associated control devices being constructed in an identical manner.

Referring to the drawing, a forging saddle l, is pivotally mounted on a pin 2 of a machine frame (not illustrated) of a forging machine, the axis of the pin 2 being parallel to the feed direction of a workpiece and extending perpendicular to the plane of the drawing.

The forging saddle 1 is actuated by a hydraulic piston and cylinder drive comprising an operating piston 4 displaceable in a driving cylinder 3'and engaging the rear side of the forging saddle l. The piston 4 is limited in itsrearward end position, illustrated in the drawing, by an adjustable abutment device 5. In the illustration embodiment the abutment device 5 consists of a doubleacting piston and cylinder device having a hydraulic cylinder 6 and a piston 7 which is displaceable in the cylinder 6 and has two oppositely directed piston rods 8 and 9. The lower piston rod 8 projects from the hydraulic cylinders 6 to form the abutment proper since the operating piston 4 rests in its rearward end position on the piston rod 8. Non-return valves 13, 14, which permit fluid flow into the hydraulic cylinder 6 are disposed in two control pipes ll, 12. connected to the hydraulic cylinder 6 and to a source (not shown) of fluid under pressure. A piston rod 16 is connected to a piston displaceable in a retraction cylinder 17 engages'a bearing eye 15 of the-forging saddle l, the retraction cylinder 17 serving to return the operating piston 4 after each forging stroke into its starting position in which the piston abuts the pistonrod 8 of the abutment device 5. The retraction cylinder 17 is connected through a feed pipe 18 to a source 19 of fluid under pressure, which maintains a constant pressure in the retraction cylinder 17. i

The operating piston 4 of the operating cylinder 3 can be subjected to fluid pressure bya pump cylinder 22 to which it is connected through a connecting pipe 21. A piston 23 which is displaceably mounted in the cylinder 22 is attached to a yoke 24 which is connected to a driving arrangement 26 by means of a connecting rod 25. In the illustrated embodiment the driving arrangement 26 consists of a single throw crank drive which is driven through a gear (not shown) by a motor (not shown). The crank drive 26 comprises a rotating shaft 27attached to a control element 28, the purpose of which is described in detail below.

A pressure store 31 isconnected to a branch pipe 29 of the connecting pipe 21, and anon-"return valve 32, which is controllable by the crank drive 26 and which opens towards the connecting pipe 21, is disposed between the pressure store 31 and connecting pipe 21.. A further branch pipe 33 of the connecting pipe 21 terminates in a control space 34 of a compensating cylinder 35. The compensating cylinder 35 accommodates a displaceable piston 36 with oppositely directed piston rods 37 and 38 attached thereto. The lower piston rod 38 extends to the exterior of the compensating cylinder 35 and the other piston rod 37 projects into the control] space 34 and seals the latter in a fluid tight manner from the adjacent operating space of the compensating cylinder 35. The two operating chambers of the compensating cylinder 35 are connected through respective control pipes 39, 41 to a servo-valve 42 .which is constructed as a multiple path valve and which is connected to a fluid tank 43 and a control pump 44.

The servo-valve 42 is controllable by means of a controller-46 which can deliver an impulse thereto via an electrical conductor 45 dependently upon an actual valve/nominal valve comparison. By means of a further conductor 47 the controller 46 is connected to a transmitter 48 which co-operates with a pinion 49 engaging a toothed rack 51. The rack 51 is disposed at the free end of a lever 52 the other end of which is rigidly connected to the pin 2 of the forging saddle l.

A conductor 53 leads from the controller 46 to a further actual value transmitter 54 which co-operates with a position indicator 55 disposed on the free end of the piston rod 38 projecting from the compensating cylinder 35. Further conductors 56, 57, lead to further actual value transmitters 58 and 60. The actual value transmitter 58 delivers an impulse to the controller 46 when the crank drive 26 assumes its forward end posi' tion, whereas the actual value transmitter 60 delivers an impulse to the controller 46' when the pressure in the connecting pipe 21 is low or nearly zero.

When the forging machine is started the yoke 24 and thus the piston 23 in thepump cylinder 22 are moved an equal distance to the left by means of the crank drive 26 and the connecting rod 25. The liquid so displaced passes through the connecting pipe 21 in to theoperating cylinder 3. The forging saddle l is thus rotated downwardly around its pivot pin2 by the pressure loaded operating piston 4, so that the cross section of a workpiece which is conveyed stepwise through the machine by means of manipulators (not shown) can be reduced. Since the piston 23 of the pump cylinder 22 has a smaller diameter than the operating piston 4 of the operating cylinder the forging saddle '1 performs a reduced stroke in comparison to the piston areas. It will be appreciated that the other forging saddles of the forging machine operate in the same way as described so that the workpiece is deformed by pressure acting on all sides thereof.

After the forging stroke the crank drive 26 starts its return, so thatthe piston 23 is moved back again towards the right. The fluid pressure prevailing in the pump cylinder 22 as well as in the connecting pipe 21 is thereby reduced so that the operating piston 4 can be moved back by the retraction cylinder 17 engaging the forging saddle 1. In the end :position of the return movement, the operating piston 4 rests on the piston rod 8 of the abutment device 5. The individual forging saddles of the forging machine thus move towards and away from each other with a sinosoidal speed characteristic and thereby effect the deformation of the workpiece.

During forging the position of the forging saddle 1 in respect of the workpiece to be forged is transmitted by the toothed rack 51 and the pinion 49 to the transmitter 48 and thence to the controller '46 in which the exact position of the forging saddle 1 is compared with a predetermined nominal value. If a difference exists a signal is delivered through the conductor 45 to the servo-valve 42 so that the latter travels from its closed position into its operative position to allow liquid under pressure toflow from the control pump 44 through one of the-two pipes 39, 41 into the compensating cylinder 35. The piston rod 37 is thus displaced in the control chamber 34 and the quantity of pressure fluid in the connecting pipe 21 is changed via the branch pipe 33. A change of the stroke position of the operating piston 4, which may be necessary, for example because of leakage losses, can be performed automatically during the forging by means of this control.

In order to ensure that the actual value/nominal value comparison is performed at the correct instantof time, an impulse is sent by the actual value transmitter 58 and the conductor 56 to the controller 46 when the crank drive 26 is located in its forward end position in which maximum pressure prevails in the connecting pipe and the operating piston 4 is in its extended forging position. The measurement is then made in this position by the actual value transmitter 48. The servovalve 42, however, can be controlled by the controller 46 only when an impulse is delivered through the conductor 57 to the controller 46 by the other actual value transmitter 59 which is controlled by the control element 28 on the shaft 27 of the crank drive 26, the impulse indicating that the pressure in the connecting pipe 21 is nearly zero. Only then is the servo-valve 42 I justed forging starting position and nevertheless disconnect the forging drive of the forging saddles while the crank drive 26 continues to rotate, the non-return valve 32 disposed in the branch pipe 29 is moved by the crank drive 26 into its open position. The pressure liquid displaced by the piston 23 from the pump cylinder 22 by the continuously travelling crank drive 26 then travels through the branch pipe 29 and the open valve 32 into the pressure store 31' so that the pressure is compensated, that is to say the operating piston 4 is not under pressure. The piston 4 is-retained in its adjusted starting position by the retracting cylinder 17.

Also, the pressure fluid in the connecting pipe 21 the operating cylinder 3 and the pump cylinder 22 can be changed by the pressure store 31 so that undesirable heating of the pressure liquid is avoided. L

' I claim:

1. A control device with hydraulic synchronising control for a forging machine having a plurality of forging saddles which act upon a workpiece to reduce the cross section thereof by lateral pressure respective operating piston and cylinder devices associated with the forging saddles, each piston being subjected on the one hand to the effect of a substantially constant return force and on the other hand being connected to a respective pump cylinder, a driving arrangement for periodically reciprocating the pistons of the pump cylinders, a transmitter which measures the actual position of each forging saddle, an electrical controller for comparing the measured values with a nominal value, a controllable filling pump associated with each; forging saddle and adapted to be controlled by the electrical controller to adjust the dead position of the operating cylinders so as to correspond to the farthest extension of each forging saddle, said filling pump being connected to the conduit system associated with the respective op erating cylinder and effecting the variation of the filling capacity in the conduit system in response to a comparison between the measured value and the nominal value only when the pressure in the conduit system is approximately zero upon retraction of the operating piston, wherein the filling pump for each forging saddle is a double acting compensating cylinder having an adjustable piston separating two chambers and a piston rod extending into a control chamber connected to the connection line between the pressure side of the operating cylinder and the pump cylinder of the driving arrangement. I

2. A control device according to claim 1, wherein the two operating chambers of the compensating cylinder are selectively connectable to a control pump by a multiple path control valve actuated by the controller.

3. Acontrol device according to claim 1, wherein the transmitter which measures the actual position of arespective forging saddle cooperates with a pinion which engages into a toothed rack secured to the free end of a lever attached to a pivot pin mounted on the forging saddle.

4. A control device according to claim 1 wherein the controller is electrically connected to a further actual value transmitter which co-operates with a position indicator which is disposed on a further piston rod located opposite the piston rod determining the filling capacity of the compensating cylinder and projecting from the latter.

5. A control device according to claim 1 wherein the controller is electrically connected to a transmitter which indicates the pump cylinder rear dead positions of the driving arrangement constructed as a crank drive.

, 6. A control device according to claim 5 wherein the controller is electrically connected to a transmitter which determines the fluid pressure in the connecting pipe between the operating cylinder and the pump cylinder. r

7. A control device according to claim 1, wherein the connecting pipe is adapted to be connected to'a pres-' sure store by a nonretum valve which opens towards the connecting pipe and is controllable by the crank drive. 

1. A control device with hydraulic synchronising control for a forging machine having a plurality of forging saddles which act upon a workpiece to reduce the cross section thereof by lateral pressure respective operating piston and cylinder devices associated with the forging saddles, each piston being subjected on the one hand to the effect of a substantially constant return force and on the other hand being connected to a respective pump cylinder, a driving arrangement for periodically reciprocating the pistons of the pump cylinders, a transmitter which measures the actual position of each forging saddle, an electrical controller for comparing the measured values with a nominal value, a controllable filling pump associated with each forging saddle and adapted to be controlled by the electrical controller to adjust the dead position of the operating cylinders so as to correspond to the farthest extension of each forging saddle, said filling pump being connected to the conduit system associated with the respective operating cylinder and effecting the variation of the filling capacity in the conduit system in response to a comparison between the measured value and the nominal value only when the pressure in the conduit system is approximately zero upon retraction of the operating piston, wherein the filling pump for each forging saddle is a double acting compensating cylinder having an adjustable piston separating two chambers and a piston rod extending into a control chamber connected to the connection line between the pressure side of the operating cylinder and the pump cylinder of the driving arrangement.
 2. A control device according to claim 1, whereIn the two operating chambers of the compensating cylinder are selectively connectable to a control pump by a multiple path control valve actuated by the controller.
 3. A control device according to claim 1, wherein the transmitter which measures the actual position of a respective forging saddle cooperates with a pinion which engages into a toothed rack secured to the free end of a lever attached to a pivot pin mounted on the forging saddle.
 4. A control device according to claim 1 wherein the controller is electrically connected to a further actual value transmitter which co-operates with a position indicator which is disposed on a further piston rod located opposite the piston rod determining the filling capacity of the compensating cylinder and projecting from the latter.
 5. A control device according to claim 1 wherein the controller is electrically connected to a transmitter which indicates the pump cylinder rear dead positions of the driving arrangement constructed as a crank drive.
 6. A control device according to claim 5 wherein the controller is electrically connected to a transmitter which determines the fluid pressure in the connecting pipe between the operating cylinder and the pump cylinder.
 7. A control device according to claim 1, wherein the connecting pipe is adapted to be connected to a pressure store by a non-return valve which opens towards the connecting pipe and is controllable by the crank drive. 